Exercise equipment is quickly becoming more of a part of the daily lives of people in our fast paced and yet physically sedentary lifestyle. The basic concept of resistance or strength training appears dangerous on the surface, and in some cases it is. Effective strength training must stimulate the muscles by an “overload” or by stressing the muscles to a greater degree then they are accustomed to being stressed. This typically involves using heaver weights on subsequent training sessions. As the weight increases, the potential for injury also increases. This injury may result from stressing the muscle beyond its ability to recover (overtraining) or to accommodate a specific load (muscle strain or muscle pull). These types of injuries are usually relatively minor. In these cases the body will recover within a short period. A more serious injury type is by allowing the weight to fall and impact a portion of the user's body. This can result in severe damage to the body including permanent injury or even death. In an effort to address some of these potential problems, equipment designers have come up with products that decrease the chances of injury while allowing certain movements to be performed. One such example is a “smith machine”. This machine includes an Olympic bar that allows weight plates to be received on each distal end. The bar is guided by two linear bearings or the equivalent, thus limiting the movement of the bar to one degree of freedom (substantially vertical displacement). Examples are shown of typical smith machines in the accompanied photos. The unit by LifeFitness is very standard and does not have a counterbalance to offset part of the weight of the bar. The Flex product (photo) does have a counterbalance. This allows a lighter minimum resistance for use with some exercises. The safety advantage to such a device is the linear displacement of the weighted bar. The limited freedom of movement reduces the likelihood of the bar being dropped and injuring the user.
The typical locking mechanism used includes a series of pins along the vertical rails and a pair of hooks that are mounted to the bar. The user rotates the bar to engage or disengage the hooks on the pins. When engaged, the bar hangs from the pins by way of the hooks. When disengaged, the bar is free to move, or fall. The problem is, some times the user may think the bar is hooked on the pins, when in reality it is not. The bar can be dropped and potentially severely injure the user. In other cases the user may want to engage the pins, but is not able to do so due to loosing grip with the bar, fatigue, or sustaining an injury while using the device. In each of these cases, the bar may fall and injure the user or a bystander.
The disclosed invention may also be adapted to many forms of exercise equipment and is not intended to be limited to a “smith machine” or for that matter any other linear motion device. In most cases a linear or curvilinear track is preferable and accepted in the industry. As such, these types of devices are shown for examples. Another typical device is a “hack squat” machine. Photos of typical hack squat machines from Muscle Dynamics and Hammer Strength are included for reference. These include a back support pad that is mounted to a carriage that moves relative to a base plate on which the user places their feet. The user reciprocates the movement of the carriage to exercise the muscles of the legs and hips, usually with weights added to the weight collars.